Dual Thermal Coefficient Dispensing Chamber

ABSTRACT

An injection device has a dispensing chamber housing, a plunger, and a temperature control device. The dispensing chamber housing has a first part and a second part. The first part is thermally coupled to a needle. The second part is thermally coupled to the first part. The second part has an inner surface and an outer surface. The inner surface partially defines a dispensing chamber for holding a quantity of a substance. The plunger is engaged with an inner surface of the dispensing chamber housing, is capable of sliding in the dispensing chamber housing, and is fluidly sealed to the inner surface of the dispensing chamber housing. The temperature control device at least partially surrounds the dispensing chamber housing and is capable of altering a temperature of the substance in the dispensing chamber. The second part has a greater thermal coefficient than the first part.

RELATED APPLICATIONS

This Application is a continuation-in-part of U.S. patent application Ser. No. 11/581629 filed Oct. 16, 2006 and U.S. patent application Ser. No. 11/435,906 filed May 17, 2006.

BACKGROUND OF THE INVENTION

The present invention relates to a single-use medical device and more particularly to an ophthalmic drug delivery device with a dual thermal coefficient dispensing chamber.

Several diseases and conditions of the posterior segment of the eye threaten vision. Age related macular degeneration (ARMD), choroidal neovascularization (CNV), retinopathies (e.g., diabetic retinopathy, vitreoretinopathy), retinitis (e.g., cytomegalovirus (CMV) retinitis), uveitis, macular edema, glaucoma, and neuropathies are several examples.

These, and other diseases, can be treated by injecting a drug into the eye. Such injections are typically manually made using a conventional syringe and needle. FIG. 1 is a perspective view of a prior art syringe used to inject drugs into the eye. In FIG. 1, the syringe includes a needle 105, a luer hub 110, a chamber 115, a plunger 120, a plunger shaft 125, and a thumb rest 130. As is commonly known, the drug to be injected is located in chamber 115. Pushing on the thumb rest 130 causes the plunger 120 to expel the drug through needle 105.

In using such a syringe, the surgeon is required to puncture the eye tissue with the needle, hold the syringe steady, and actuate the syringe plunger (with or without the help of a nurse) to inject the fluid into the eye. The volume injected is typically not controlled in an accurate manner because the vernier on the syringe is not precise relative to the small injection volume. Fluid flow rates are uncontrolled. Reading the vernier is also subject to parallax error. Tissue damage may occur due to an “unsteady” injection. Reflux of the drug may also occur when the needle is removed from the eye.

An effort has been made to control the delivery of small amounts of liquids. A commercially available fluid dispenser is the ULTRA™ positive displacement dispenser available from EFD Inc. of Providence, R.I. The ULTRA dispenser is typically used in the dispensing of small volumes of industrial adhesives. It utilizes a conventional syringe and a custom dispensing tip. The syringe plunger is actuated using an electrical stepper motor and an actuating fluid. Parker Hannifin Corporation of Cleveland, Ohio distributes a small volume liquid dispenser for drug discovery applications made by Aurora Instruments LLC of San Diego, Calif. The Parker/Aurora dispenser utilizes a piezo-electric dispensing mechanism. Ypsomed, Inc. of Switzerland produces a line of injection pens and automated injectors primarily for the self-injection of insulin or hormones by a patient. This product line includes simple disposable pens and electronically-controlled motorized injectors.

U.S. Pat. No. 6,290,690 discloses an ophthalmic system for injecting a viscous fluid (e.g. silicone oil) into the eye while simultaneously aspirating a second viscous fluid (e.g. perflourocarbon liquid) from the eye in a fluid/fluid exchange during surgery to repair a retinal detachment or tear. The system includes a conventional syringe with a plunger. One end of the syringe is fluidly coupled to a source of pneumatic pressure that provides a constant pneumatic pressure to actuate the plunger. The other end of the syringe is fluidly coupled to an infusion cannula via tubing to deliver the viscous fluid to be injected.

It would be desirable to have a portable hand piece for reliably injecting a drug into the eye. In the case where the drug is to be heated or cooled, it is desirable to bring the drug to the proper temperature before it is injected into the eye and to keep it at the proper temperature during the course of the injection. For example, when a heated drug is used, it is desirable to keep the drug heated until it enters the eye. Accordingly, for optimal results, the drug should remain at an elevated temperature as it travels through then needle and into the eye.

SUMMARY OF THE INVENTION

In one embodiment consistent with the principles of the present invention, the present invention is an injection device having a dispensing chamber housing, a plunger, and a temperature control device. The dispensing chamber housing has a first part and a second part. The first part is thermally coupled to a needle. The second part has an inner surface and an outer surface. The inner surface partially defines a dispensing chamber for holding a quantity of a substance. The second part is thermally coupled to the first part. The plunger is engaged with an inner surface of the dispensing chamber housing, is capable of sliding in the dispensing chamber housing, and is fluidly sealed to the inner surface of the dispensing chamber housing. The temperature control device at least partially surrounds the dispensing chamber housing and is capable of altering a temperature of the substance in the dispensing chamber. The second part has a greater thermal coefficient than the first part.

In another embodiment consistent with the principles of the present invention, the present invention is a dispensing chamber housing for an injection device. The housing has a first part and a second part. The first part is thermally coupled to a needle. The second part is thermally coupled to the first part. The second part has an inner surface and an outer surface. The inner surface partially defines a dispensing chamber for holding a quantity of a substance. The first part is less thermally conductive than the second part.

In another embodiment consistent with the principles of the present invention, the present invention is an injection device having a dispensing chamber housing, a plunger, a temperature control device, a power source for providing power to the temperature control device, and a controller for controlling the temperature control device. The dispensing chamber housing has a first part and a second part. The first part is thermally coupled to a needle. The second part has an inner surface and an outer surface. The inner surface partially defines a dispensing chamber for holding a quantity of a substance. The second part is thermally coupled to the first part. The plunger is engaged with an inner surface of the dispensing chamber housing, is capable of sliding in the dispensing chamber housing, and is fluidly sealed to the inner surface of the dispensing chamber housing. The temperature control device at least partially surrounds the dispensing chamber housing and is capable of altering a temperature of the substance in the dispensing chamber. The second part has a greater thermal coefficient than the first part.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are intended to provide further explanation of the invention as claimed. The following description, as well as the practice of the invention, set forth and suggest additional advantages and purposes of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate several embodiments of the invention and together with the description, serve to explain the principles of the invention.

FIG. 1 is a perspective view of a prior art syringe.

FIG. 2 is one view of an ophthalmic medical device including a disposable tip segment and a limited reuse assembly according to an embodiment of the present invention.

FIG. 3 is another embodiment of a limited reuse assembly according to the principles of the present invention.

FIG. 4 is a cross section view of a disposable tip segment and a limited reuse assembly according to an embodiment of the present invention.

FIG. 5 is an exploded cross section view of a tip segment for an ophthalmic medical device according to an embodiment of the present invention.

FIGS. 6A and 6B are exploded cross section views of a dual thermal coefficient dispensing chamber according to the principles of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reference is now made in detail to the exemplary embodiments of the invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers are used throughout the drawings to refer to the same or like parts.

FIG. 2 is one view of an ophthalmic medical device including a disposable tip segment and a limited reuse assembly according to an embodiment of the present invention. In FIG. 2, the medical device includes a tip segment 205 and a limited reuse assembly 250. The tip segment 205 includes a needle 210, a housing 215, and an optional light 275. The limited reuse assembly 250 includes a housing 255, a switch 270, a lock mechanism 265, and a threaded portion 260.

Tip segment 205 is capable of being connected to and removed from limited reuse assembly 250. In this embodiment, tip segment 205 has a threaded portion on an interior surface of housing 215 that screws onto the threaded portion 260 of limited reuse assembly 250. In addition, lock mechanism 265 secures tip segment 215 to limited reuse assembly 250. Lock mechanism 265 may be in the form of a button, a sliding switch, or a cantilevered mechanism. Other mechanisms for connecting tip segment 205 to limited reuse assembly 250, such as those involving structural features that mate with each other, are commonly known in the art and are within the scope of the present invention.

Needle 210 is adapted to deliver a substance, such as a drug, into an eye. Needle 210 may be of any commonly known configuration. Preferably, needle 210 is designed such that its thermal characteristics are conducive to the particular drug delivery application. For example, when a heated drug is to be delivered, needle 210 may be relatively short (several millimeters) in length to facilitate proper delivery of the drug.

Switch 270 is adapted to provide an input to the system. For example, switch 270 may be used to activate the system or to turn on a heater. Other switches, buttons, or user-directed control inputs are commonly known and may be employed with limited reuse assembly 250 and/or tip segment 205.

Optional light 275 is illuminated when tip segment 205 is ready to be used. Optional light 275 may protrude from housing 215, or it may be contained within housing 215, in which case, optional light 275 may be seen through a clear portion of housing 215. In other embodiments, optional light 275 may be replaced by an indicator, such as a liquid crystal display, segmented display, or other device that indicates a status or condition of disposable tip segment 205. For example, optional light 275 may also pulse on and off to indicate other states, such as, but not limited to a system error, fully charged battery, insufficiently charged battery or faulty connection between the tip segment 205 and limited use assembly 250. While shown on tip segment 205, optional light 275 or other indicator may be located on limited reuse assembly 250.

FIG. 3 is another embodiment of a limited reuse assembly according to the principles of the present invention. Limited reuse assembly 250 includes a button 308, a display 320, and a housing 330. Disposable tip segment 205 attaches to end 340 of limited reuse assembly 250. Button 308 is actuated to provide an input to the system. As with switch 270, button 308 may activate a heater or other temperature control device or initiate actuation of a plunger. Display 320 is a liquid crystal display, segmented display, or other device that indicates a status or condition of disposable tip segment 205 or limited reuse assembly 250.

FIG. 4 is cross section view of a disposable tip segment and a limited reuse assembly according to an embodiment of the present invention. FIG. 4 shows how tip segment 205 interfaces with limited reuse assembly 250. In the embodiment of FIG. 4, tip segment 205 includes plunger interface 420, plunger 415, dispensing chamber housing 425, tip segment housing 215, temperature control device 450, thermal sensor 460, needle 210, dispensing chamber 405, interface 530, and tip interface connector 453. Limited reuse assembly 250 includes mechanical linkage interface 545, actuator shaft 510, actuator 515, power source 505, controller 305, limited reuse assembly housing 255, interface 535, and limited reuse assembly interface connector 553.

In tip segment 205, plunger interface 420 is located on one end of plunger 415. The other end of plunger 415 forms one end of dispensing chamber 405. Plunger 415 is adapted to slide within dispensing chamber 405. The outer surface of plunger 415 is fluidly sealed to the inner surface of dispensing chamber housing 425. Dispensing chamber housing 425 surrounds the dispensing chamber 405. Typically, dispensing chamber housing 425 has a cylindrical shape. As such, dispensing chamber 405 also has a cylindrical shape. Dispensing chamber housing 425 is made of two parts as described below.

Needle 210 is fluidly coupled to dispensing chamber 405. In such a case, a substance contained in dispensing chamber 405 can pass through needle 210 and into an eye. Temperature control device 450 at least partially surrounds dispensing chamber housing 425. In this case, temperature control device 450 is adapted to heat and/or cool dispensing chamber housing 425 and any substance contained in dispensing chamber 405. Interface 530 connects temperature control device 450 with tip interface connector 453.

Optional thermal sensor 460 provides temperature information to assist in controlling the operation of temperature control device 450. Thermal sensor 460 may be located near dispensing chamber housing 425 and measure a temperature near dispensing chamber housing 425 or may be located in thermal contact with dispensing chamber housing 425, in which case it measures a temperature of dispensing chamber housing 425. Thermal sensor 460 may be any of a number of different devices that can provide temperature information. For example, thermal sensor 460 may be a thermocouple or a resistive device whose resistance varies with temperature. Thermal sensor is also electrically coupled to interface 530 or other similar interface.

The components of tip segment 205, including dispensing chamber housing 425, temperature control device 450, and plunger 415 are at least partially enclosed by tip segment housing 215. In one embodiment consistent with the principles of the present invention, plunger 415 is sealed to the interior surface of dispensing chamber housing 425. This seal prevents contamination of any substance contained in dispensing chamber 405. For medical purposes, such a seal is desirable. This seal can be located at any point on plunger 415 or dispensing chamber housing 425.

In limited reuse assembly 250, power source 505 provides power to actuator 515. An interface (not shown) between power source 505 and actuator 515 serves as a conduit for providing power to actuator 515. Actuator 515 is connected to actuator shaft 510. When actuator 515 is a stepper motor, actuator shaft 510 is integral with actuator 515. Mechanical linkage interface 545 is connected to actuator shaft 510. In this configuration, as actuator 515 moves actuator shaft 510 upward toward needle 210, mechanical linkage interface 545 also moves upward toward needle 210. In other embodiments of the present invention, mechanical linkage interface 545 and actuator shaft 510 are a single component. In other words, a shaft connected to actuator 515 includes both actuator shaft 510 and mechanical linkage interface 545 as a single assembly.

In limited reuse assembly 250, power source 505 is typically a rechargeable battery, such as a lithium ion battery, although other types of batteries may be employed. In addition, any other type of power cell is appropriate for power source 505. Power source 505 provides current to dispensing chamber housing 425 to heat it and change its shape. Optionally, power source 505 can be removed from housing 255 through a door or other similar feature (not shown).

Controller 305 is connected via interface 535 to limited reuse assembly interface connecter 553. Limited reuse assembly interface connecter 553 is located on a top surface of limited reuse assembly housing 255 adjacent to mechanical linkage interface 545. In this manner, both limited reuse assembly interface connector 553 and mechanical linkage interface 545 are adapted to be connected with tip interface connector 453 and plunger interface 420, respectively.

Controller 305 and actuator 515 are connected by an interface (not shown). This interface (not shown) allows controller 305 to control the operation of actuator 515. In addition, an interface between power source 505 and controller 305 allows controller 305 to control operation of power source 505. In such a case, controller 305 may control the charging and the discharging of power source 505 when power source 505 is a rechargeable battery.

Controller 305 is typically an integrated circuit with power, input, and output pins capable of performing logic functions. In various embodiments, controller 305 is a targeted device controller. In such a case, controller 305 performs specific control functions targeted to a specific device or component, such as a temperature control device or a power supply. For example, a temperature control device controller has the basic functionality to control a temperature control device. In other embodiments, controller 305 is a microprocessor. In such a case, controller 305 is programmable so that it can function to control more than one component of the device. In other cases, controller 305 is not a programmable microprocessor, but instead is a special purpose controller configured to control different components that perform different functions. While depicted as one component in FIG. 5, controller 305 may be made of many different components or integrated circuits.

Tip segment 205 is adapted to mate with or attach to limited reuse assembly 250. In the embodiment of FIG. 4, plunger interface 420 located on a bottom surface of plunger 415 is adapted to mate with mechanical linkage interface 545 located near a top surface of limited reuse assembly housing 255. In addition, tip interface connector 453 is adapted to connect with limited reuse assembly interface connector 553. When tip segment 205 is connected to limited reuse assembly 250 in this manner, actuator 515 and actuator shaft 510 are adapted to drive plunger 415 upward toward needle 210. In addition, an interface is formed between controller 305 and temperature control device 450. A signal can pass from controller 305 to temperature control device 450 through interface 535, limited reuse assembly interface connector 553, tip interface connector 453, and interface 530.

In operation, when tip segment 205 is connected to limited reuse assembly 250, controller 305 controls the operation of actuator 515. When actuator 515 is actuated, actuator shaft 510 is moved upward toward needle 210. In turn, mechanical linkage interface 545, which is mated with plunger interface 420, moves plunger 415 upward toward needle 210. A substance located in dispensing chamber 405 is then expelled through needle 210.

In addition, controller 305 controls the operation of temperature control device 450. Temperature control device 450 is adapted to heat and/or cool dispensing chamber housing 425 and its contents. Since dispensing chamber housing 425 is at least partially thermally conductive, heating or cooling dispensing chamber housing 425 heats or cools a substance located in dispensing chamber 405. Temperature information can be transferred from thermal sensor 460 through interface 530, tip interface connector 453, limited reuse assembly interface connector 553, and interface 535 back to controller 305. This temperature information can be used to control the operation of temperature control device 450. When temperature control device 450 is a heater, controller 305 controls the amount of current that is sent to temperature control device 450. The more current sent to temperature control device 450, the hotter it gets. In such a manner, controller 305 can use a feed back loop utilizing information from thermal sensor 460 to control the operation of temperature control device 450. Any suitable type of control algorithm, such as a proportional integral derivative (PID) algorithm, can be used to control the operation of temperature control device 450.

A substance to be delivered into an eye, typically a drug suspended in a phase transition compound, is located in dispensing chamber 405. In this manner, the drug and phase transition compound are contacted by the inner surface of dispensing chamber housing 425. The phase transition compound is in a solid or semi-solid state at lower temperatures and in a more liquid state at higher temperatures. Such a compound can be heated by the application of current to temperature control device 450 to a more liquid state and injected into the eye where it forms a bolus that erodes over time.

Likewise, a reverse gelation compound may be used. A reverse gelation compound is in a solid or semi-solid state at higher temperatures and in a more liquid state at lower temperatures. Such a compound can be cooled by temperature control device 450 to a more liquid state and injected into the eye where it forms a bolus that erodes over time. As such, temperature control device 450 may be a device that heats a substance in dispensing chamber 405 or a device that cools a substance in dispensing chamber 405 (or a combination of both). After being delivered into the eye, a phase transition compound or reverse gelation compound erodes over time providing a quantity of drug over an extended period of time. Using a phase transition compound or reverse gelation compound provides better drug dosage with fewer injections.

In one embodiment of the present invention, the substance located in dispensing chamber 405 is a drug that is preloaded into the dispensing chamber. In such a case, tip segment 205 is appropriate as a single use consumable product. Such a disposable product can be assembled at a factory with a dosage of a drug installed.

While shown as a two-piece device, the injection system of FIG. 4 may be a single piece device. In such a case, the tip segment is integrated into the limited reuse assembly to form a single medical device.

FIG. 5 is an exploded cross section view of a tip segment for an ophthalmic medical device according to an embodiment of the present invention. In FIG. 5, tip segment 205 includes a dispensing chamber housing that has a first part 610 and a second part 620, tip segment housing 215, thermal sensor 460, needle 210, dispensing chamber 405, plunger 415, plunger interface 420, temperature control device 450, interface 530, and tip interface connector 453.

In the embodiment of FIG. 5, temperature control device 450 is activated to bring a substance in dispensing chamber 405 to within a proper temperature range. Thermal sensor 460 provides temperature information to controller 305 (not shown) to control temperature control device 450. After the substance has reached the proper temperature range, plunger 415 is actuated to deliver the substance through needle 210 and into an eye.

The dispensing chamber housing is made of two components—a first part 610 and a second part 620. Typically, both the first and second parts 610, 620 are generally cylindrical in shape and fit together to form a dispensing chamber housing capable of holding a substance. When first part 610 is fitted with second part 620, a liquid-tight seal is formed. First part 610 and second part 620 are made of different materials. Each of the two different materials has a different thermal coefficient (used herein to characterize a material's ability to conduct heat—also known as the thermal conductivity of a material). The first part 610 has a lower thermal coefficient (and is capable of conducting less heat) than the second part 620. The first part 610 is thermally coupled to needle 210 (which is typically made of stainless steel). The second part 620 primarily surrounds dispensing chamber 405 and the substance contained therein.

When thermal control device 450 is a heater or peltier, heat is applied to the first part 610. First part 610 conduct heat to second part 620 from thermal control device 450. However, since first part 610 has a lower thermal coefficient than second part 620, first part 610 can be made to be hotter than second part 620 (at least for a period of time). Since first part 610 is thermally coupled to needle 210, needle 210 is maintained at a temperature equal to or below first part 610 but higher than second part 620. In this manner, thermal control device 450 can be used to heat a substance to a lower temperature range while keeping needle 210 at a higher temperature. In other words, heat from thermal control device 450 is conducted by second part 620 to heat the substance contained in dispensing chamber 405 and is conducted by first part 610 to heat needle 210. Since first part 610 has a lower thermal coefficient than second part 620, needle 210 is kept at a higher temperature than the substance that is surrounded primarily by second part 620. This allows for the injection substance to maintain its liquid state while being injected, while needle 210 is at a temperature which will prevent the substance from cooling too quickly. The lower thermal conductivity of needle 210 prevents the tissue it has pierced from being adversely affected.

In various embodiments, temperature control device 450 may be in thermal contact with both first part 610 and second part 620 or only with first part 610. Since first part 610 is in thermal contact with second part 620, heat may be conducted from first part 610 to second part 620. Since second part 620 has a higher thermal conductivity than first part 610, the heat transfer from first part 610 to second part 620 is limited, allowing for a temperature gradient (610 will have a higher temperature than 620) However, first part 610 will maintain its temperature more readily than second part 620 due to its lower thermal conductivity.

When the substance is a drug suspended in a phase transition compound, such an arrangement is beneficial. Keeping needle 210 at the same temperature or hotter than the phase-transition compound ensures that it will not cool too readily and clog needle 210. Since a phase transition compound is heated to a liquid or semi-liquid state for injection into an eye, it should be maintained in that liquid or semi-liquid state until it enters the eye (where the eye acts like a heat sink and rapidly cools the phase transition compound to form a bolus that erodes over time). Keeping the needle at or above the temperature of the phase transition compound while it is in a liquid or semi-liquid state allows the phase transition compound to pass easily through needle 210. If needle 210 were much cooler than the phase transition compound, then it would clog as the phase transition compound cools inside needle 210. Utilizing a dispensing chamber housing made of first part 610 and second part 620 with different thermal coefficients allows needle 210 to be maintained at a suitably heated temperature and allows the drug to be heated to an equal or lower temperature.

Typically needle 210 is a small gauge needle (such as a 25 gauge needle). Such a small gauge needle cools if exposed to ambient air. As such first part 610 (with a lower thermal coefficient than second part 620) retains heat and keeps needle 210 at a suitably high temperature to facilitate injection of a phase transition compound into the eye.

The same principles hold true for a reverse gelation compound. In this case, it is desirable to keep needle 210 cool so that a reverse gelation compound can pass through needle 210 without clogging it. The same arrangement of first part 610 and second part 620 allows needle 210 to be kept cool when temperature control device 450 performs a cooling function. The lower thermal conductivity of needle 210 prevents it from being readily heated by the tissue it comes in contact with.

Any number of different materials may be selected to construct first part 610 and second part 620. These materials may both be metals (or alloys thereof) or non-metals or a combination of metals and non-metals. Examples of different materials (with a range for their thermal coefficient in parentheses) include: Aluminum (205-237); Brass (109-159); Bronze (42-50); Copper (385-401); Gold (314-318); Silver (406-429); Stainless steel (14-16); Titanium (16-22); Titanium Alloy (5-6); Diamond (900-2320); Glass (0.8-1.4); and Polymers (0.3-0.5) where the thermal coefficient is a measure of thermal conductivity in watts per Kelvin meter. This list merely presents examples. Any number of different materials may be employed and are within the scope of this invention. In one embodiment of the present invention, first part 610 is made of stainless steel and second part 620 is made of aluminum.

FIGS. 6A and 6B are exploded cross section views of a dual thermal coefficient dispensing chamber according to the principles of the present invention. As shown, first part 610 is thermally connected to needle 210. Second part 620 primarily surrounds dispensing chamber 405. First part 610 and second part 620 are fitted together to form a liquid-tight seal for dispensing chamber 405. First part 610 has a lower thermal coefficient (and is less thermally conductive) than second part 620.

From the above, it may be appreciated that the present invention provides an improved system for delivering precise volumes of a substance. The present invention provides an injection device with a dispensing chamber housing made of two parts—each with a different thermal coefficient. This allows the needle to be maintained at a proper temperature for effective delivery of the drug. The present invention is illustrated herein by example, and various modifications may be made by a person of ordinary skill in the art.

Other embodiments of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the invention being indicated by the following claims. 

1. An injection device comprising: a dispensing chamber housing having a first part and a second part, the first part thermally coupled to a needle, the second part having an inner surface and an outer surface, the inner surface partially defining a dispensing chamber for holding a quantity of a substance, the second part thermally coupled to the first part; a plunger engaged with an inner surface of the dispensing chamber housing, the plunger capable of sliding in the dispensing chamber housing, the plunger fluidly sealed to the inner surface of the dispensing chamber housing; and a temperature control device at least partially surrounding the dispensing chamber housing, the temperature control device for altering a temperature of the substance in the dispensing chamber; wherein the second part has a greater thermal coefficient than the first part.
 2. The device of claim 1 further comprising: a power source for providing power to the temperature control device.
 3. The device of claim 2 further comprising: a controller for controlling the temperature control device.
 4. The device of claim 3 further comprising: a thermal sensor located near the dispensing chamber housing, the thermal sensor for measuring a temperature.
 5. The device of claim 4 wherein the controller uses the measured temperature to control the temperature control device.
 6. The device of claim 1 wherein the first part and second parts are made of different metals.
 7. The device of claim 1 wherein the first part is made of a metal selected from the group consisting of steel, stainless steel, titanium, and alloys thereof, and the second part is made of a metal selected from the group consisting of copper, gold, silver, aluminum, and alloys thereof.
 8. The device of claim 1 wherein the needle is kept at a temperature at or above a temperature at which the substance is kept.
 9. The device of claim 1 wherein the first part has a thermal coefficient in the range of about 5 to 50 and the second part has a thermal coefficient in the range of about 100-500.
 10. The device of claim 1 wherein the first part is made of a material whose thermal conductivity is less than that of the second part.
 11. The device of claim 1 wherein the temperature control device is a heater.
 12. The device of claim 1 wherein the substance is a drug for treating a condition of the eye.
 13. The device of claim 1 wherein the power source is a rechargeable battery.
 14. A dispensing chamber housing for an injection device comprising: a first part thermally coupled to a needle; and a second part having an inner surface and an outer surface, the inner surface partially defining a dispensing chamber for holding a quantity of a substance, the second part thermally coupled to the first part; wherein the first part is less thermally conductive than the second part.
 15. The device of claim 13 wherein the first part and second parts are made of different materials.
 16. The device of claim 13 wherein the first part is made of a material selected from the group consisting of glass, polymers, steel, stainless steel, titanium, and alloys thereof, and the second part is made of a material selected from the group consisting of copper, gold, silver, aluminum, and alloys thereof.
 17. The device of claim 13 wherein the first part has a thermal coefficient in the range of about 5 to 50 and the second part has a thermal coefficient in the range of about 100-500.
 18. The device of claim 1 wherein the first part has a thermal conductivity less than that of the second part.
 19. The device of claim 13 wherein the needle is kept at a temperature at or above a temperature at which the substance is kept.
 20. An injection device comprising: a dispensing chamber housing having a first part and a second part, the first part thermally coupled to a needle, the second part having an inner surface and an outer surface, the inner surface of the second part partially defining a dispensing chamber for holding a quantity of a substance; a plunger engaged with an inner surface of the dispensing chamber housing, the plunger capable of sliding in the dispensing chamber housing, the plunger fluidly sealed to the inner surface of the dispensing chamber housing; a temperature control device at least partially surrounding the dispensing chamber housing, the temperature control device for altering a temperature of the substance in the dispensing chamber; a power source for providing power to the temperature control device; and a controller for controlling the temperature control device; wherein the first part is less thermally conductive than the second part.
 21. The device of claim 18 wherein the first part and second parts are made of different materials.
 22. The device of claim 18 wherein the first part is made of a metal selected from the group consisting of glass, polymers, steel, stainless steel, titanium, and alloys thereof, and the second part is made of a metal selected from the group consisting of copper, gold, silver, aluminum, and alloys thereof.
 23. The device of claim 18 wherein the first part has a thermal coefficient in the range of about 5 to 50 and the second part has a thermal coefficient in the range of about 100-500.
 24. The device of claim 1 wherein the first part has a thermal conductivity less than that of the second part.
 25. The device of claim 18 wherein the needle is kept at a temperature at or above a temperature at which the substance is kept.
 26. The device of claim 18 wherein the substance is a drug for treating a condition of the eye. 